Escobaria chlorantha

Escobaria chlorantha is a somewhat confusing species. Is usually mixed up with Mammillaria desetii, a species common in near and West of Las Vegas, which was described 2 years later, and a significantly different even if likely related plant. The type locality for E. desertii is Ivanpah, a place of now days solar energy project just West of CA-NV border.
Escobaria chlorantha was described by Engelmann in 1878 as Mammillaria, with type locality East of Saint George, some 100 plus miles East of Vegas. Saint George is a much large place now then back in Engelmann's time. The plant pictured is from just West of Saint George and matches the original description well, so I'm assuming it belongs to same population.
This species is not well presented in collections. This is one of the larger Escobarias. Yong plants are very pretty and different from any other in the genus, densely wrapped with long needle-like gray-pink bi-colored spines. Larger plants develop more stiff spines and darker gray shaggy look. Flowers are remarkable, relatively large (original description states controversial "small 35mm broad") and yellow as in the picture. To fully open they need lots of heat.
This species unlike the common in collection Escbarias from Mexico and Eastern US deserts does not take the 'common' cactus culture well, and need to be treated more like Echinomastus johnsonii, growing in the same area. That of cause means no summer water, but plenty if it in late winter and spring, and pure mineral pot media. With this conditions met and lots of sun plants thrive in pot culture. Seed growing is also tricky, as at some point tiny plant will not take summer watering well.